Generally, a liquid crystal display (LCD) is widely used in display devices such as laptop computers, desktop computers and TVs because the advantages are that it achieves lightweight, compact design and low power consumption. However, a LCD is not a device that produces light by itself, and is a light receiving device requiring a LCD screen as well as a backlight unit.
FIG. 1 is a schematic cross-sectional view of a LCD according to the related art.
Referring to FIG. 1, a conventional LCD 1 includes a liquid crystal panel 10, a backlight unit 20, a cover bottom 30, a guide panel 40, and a top case 50.
The liquid crystal panel 10 includes a thin film transistor substrate 12 and a color filter substrate 14 bonded to each other with a liquid crystal layer interposed between. Furthermore, polarizing members 16, 18 may be attached to a lower surface and an upper surface of the liquid crystal panel 10. Furthermore, the backlight unit 20 includes a reflection sheet 21, a light source 23 that provides light to the liquid crystal panel 10, a light guide plate 25, multiple optical sheets 27, and a housing 29 that supports the light source 23.
The cover bottom 30 has a receiving space inside to receive the light source 23, the reflection sheet 21, the light guide plate 25, and the optical sheets 27 with supporting the guide panel 40. The guide panel 40 supports the liquid crystal panel 10, and includes a panel support that supports the liquid crystal panel 10 and sidewalls that cover the backlight unit 20 as shown in FIG. 1. The top case 50 covers not only the edges of the upper surface of the liquid crystal panel 10 but also the side surfaces of the guide panel 40 and the cover bottom 30.
Here, the light guide plate 25 directs light from the light source 23 toward the liquid crystal panel 10, and is primarily made of polymer such as polymethylmethacrylate (PMMA) or polycarbonate (PC). The light guide plate 25 is a key component of the backlight unit 20 to create a surface light source by uniformly diffusing light from the side light source 23 upwards with minimum light loss.
However, PMMA primarily used for the light guide plate 25 in the related art deforms and produces harmful volatile organic compounds at high temperature (90° C.). Furthermore, PMMA has a high coefficient of thermal expansion (CTE) of about 50˜100×10−6/K, which is a limitation in reducing the width of a bezel or a non-display area of the liquid crystal panel 10. In addition, due to polymer having low mechanical strength, the guide panel 40 or a metal frame is additionally used to enhance the mechanical strength.
Accordingly, there is the demand for a light guide plate that is resistant to deformation and does not produce toxic gas in a high temperature environment during use, ensuring high-temperature stability, has a low coefficient of thermal expansion, shows high mechanical strength, eliminating the need for a metal frame, and is advantageous for production of thinner display devices, and its fabrication.
Currently, many studies are being made on new products using a glass light guide plate. Generally, glass has better mechanical properties and thermal durability than polymer, but glass absorbs more light than polymer due to the properties of the material itself, failing to efficiently transmit light from a backlight unit.